The present disclosure relates to prosthetic heart valves. More particularly, it relates to stented prosthetic heart valves and methods for making the same.
All four of the valves in the heart are passive structures in that they do not themselves expend any energy and do not perform any active contractile function. They consist of moveable “leaflets” that open and close in response to differential pressures on either side of the valve. The problems that can develop with valves can generally be classified into two categories: (1) stenosis, in which a valve does not open properly, and (2) insufficiency (also called regurgitation), in which a valve does not close properly. Stenosis and insufficiency may occur concomitantly in the same valve or in different valves. Both of these abnormalities increase the workload placed on the heart. The severity of this increased stress on the heart and the patient, and the heart's ability to adapt to it, determine the treatment options that can be pursued. In some cases, medication can be sufficient to treat the patient, which is the preferred alternative; however, in many cases defective valves have to repaired or completely replaced in order for the patient to live a normal life.
The two general categories of valves that are available for implantation into the cardiac system are mechanical valves and bioprosthetic or tissue valves. Mechanical valves have been used for many years and encompass a wide variety of designs that accommodate the blood flow requirements of the particular location where they will be implanted. Although the materials and design features of these valves are continuously being improved, they may increase the risk of clotting in the blood stream, which can lead to a heart attack or stroke. Thus, mechanical valve recipients must take anti-coagulant drugs for life to lessen the potential for blood clot formation. Further, mechanical valves can sometimes suffer from structural problems that may force the patient to have additional surgeries for further valve replacement.
Bioprosthetic valves, which are also referred to as prosthetic valves, generally include both human tissue valves and animal tissue valves. The designs of these bioprosthetic valves are typically relatively similar to the design of the natural valves of the patient and advantageously do not require the use of long-term anti-coagulant drugs. Animal tissue valves are widely available to patients who require valve replacement. The most common types of animal tissue valves used include porcine aortic valves, and bovine and porcine pericardial valves.
In general terms, prosthetic heart valve fabrication requires leaflets to be cut in a predetermined geometry from animal-derivative tissue (e.g., porcine pericardium) and then sewn or otherwise connected together. In many instances the cut leaflets are mounted to a frame, such as a metal stent. A number of different techniques and methods have been used to incorporate the tissue valve leaflets to the stent, such as clamping, tying, gluing, or stitching, for example. Many of the techniques used for this purpose generally produce a stented prosthetic heart valve that has concentrated stresses at the points where the leaflets are attached to the stent frame. That is, because the stents are relatively rigid as compared to the flexible material from which the leaflets of the tissue valve are made, the repetitive flexing motion of the leaflets can create stress concentrations at the points where the tissue valve is attached to the stent. Further, the stent typically must incorporate special design features (e.g., unique slots that serve as commissure connection points) solely for attachment of the tissue leaflets, in manner that orients the coaptation edges of the leaflets in an aligned arrangement.
In light of the above, a need exists for methods and devices for a durable attachment between a tissue valve and a stent in the manufacture of a stented prosthetic heart valve.